Diagnosis and treatment of non-infectious and infectious foal diarrhoea

Abstract

Diarrhoea is a common problem affecting foals of all ages. Common non-infectious causes of mild to moderate diarrhoea include foal heat diarrhoea and nutritionally induced diarrhoea. Clinical signs often resolve spontaneously without or with only minimal treatment. Gastroduodenal ulceration rarely presents as diarrhoea and resolves once the underlying cause is corrected. Neonatal foals may suffer from hypoxic-ischaemic enteropathy and necrotising enterocolitis; both are associated with severe, often multi-systemic disease and require intensive medical therapy. Long established infectious causes of foal diarrhoea include rotavirus, Salmonella spp. and Cryptosporidium. Diagnosis can be established using commercially available assays, consecutive faecal cultures or PCR and acid fast faecal staining, respectively. Recent evidence suggests that Clostridium difficile and perfringens may be part of the normal gastrointestinal flora of equine neonates, but can also be associated with cases of mild to severe, and even fatal diarrhoea. Due to their occurrence in normal and diseased animals, diagnosis is difficult and further investigations are required to document their role in foal diarrhoea. Correction of fluid, electrolyte and acid-base abnormalities is the most important treatment of diarrhoea regardless of the underlying aetiology and, depending on age and physiological status, systemic antimicrobials and nutritional support. Although controlled clinical trials are lacking, there is some limited evidence suggesting that treatment with metronidazole, di-tri-octahedral smectite and Saccharomyces boulardii may be beneficial in foals suffering from clostridial diarrhoea. Infectious agents affecting older foals include small strongyles and Lawsonia intracellularis, both more recently recognized pathogen causing weight loss, severe hypoproteinaemia and mild to severe diarrhoea. While diagnosis of cyathostomiasis is difficult to establish intra vitam, L. intracellularis may be diagnosed by serology or identification of the organism by faecal PCR. Treatment consists of larvicidal doses of fenbendazole and systemic antimicrobials with excellent intracellular penetration, respectively.